Dissertations / Theses on the topic 'Sound – Speed – Measurement'

A hemispherical acoustic resonator is described which was designed and constructed for the measurement of the speed of sound in gases, at pressures up to 40 MPa and at temperatures in the range from 300 K to 400 K. The hemispherical geometry retains many of the advantages characteristic of the spherical geometry but affords a major advantage at high pressures because one of the transducers may be placed at a position of maximum acoustic density for the radial modes and so loss of signal strength is minimised. A detailed description is given of the resonator and pressure vessel, the thermostat and the various measurement techniques employed. Characterisation of the resonator was achieved using a prototype equatorial plate for which the sound source could be moved over the radius of the cavity. Using the prototype plate, measurements performed in air at room temperature and pressure allowed the transducer configuration to be optimised. Calibration of the resonator was possible by comparison of the values of ula(pj) obtained isothermally in nitrogen with data obtained previously using a spherical resonator. These measurements allowed the resonator's geometry to be characteriseda nd the dependenceo f the radius on temperaturea nd pressuret o be modelled. The semi-empirical model developed using the results of the calibration was tested using measurements obtained in argon; results were obtained simultaneously from the hemispherical resonator and a well-characterised spherical resonator. Measurements on propene together with the results from nitrogen allowed the halfwidths to be modelled and enabled useful information about the loss mechanisms occurring to be extracted from the measured halfwidths. Tetrafluoromethane was subsequently studied and the acoustic virial coefficients and vibrational relaxation times were measured and compared with literature values.

The first part of the study was to characterise the acoustic properties of an IEC agar-based tissue mimicking material (TMM) at ultrasound frequencies centred around 20 MHz. The TMM acoustic properties measured were the amplitude attenuation coefficient (dB cm-1MHz-1), the sound speed (ms-1) and the backscattered power spectral density characteristics of spectral slope (dB MHz-1), y-axis intercept (dB) and reflected power (dB). The acoustic properties were measured over a temperature range of 22 - 37oC. Both the attenuation coefficient and sound speed, both group and phase, showed good agreement with the expected values of 0.5 dB cm-1 MHz-1 and 1540 ms-1 respectively with average values of 0.49 dB cm-1MHz-1 (st.dev. ± 0.03) and 1541.9 ms-1 (st.dev. ± 8.5). Overall, this non-commercial agar-based TMM was shown to perform as expected at the higher frequency range of 17-23 MHz and was seen to retain its acoustic properties of attenuation and speed of sound over a three year period. For the second part of the study, composite sound speed was measured in carotid plaque embedded in TMM. The IEC TMM was adapted to a clear agar gel. The contour maps from the attenuation plots were used to match the composite sound speed data to the photographic mask of plaque outline and thus the histological data. By solution of sets of simultaneous equations using a matrix inversion, the individual speed values for five plaque components were derived; TMM, elastin, fibrous/collagen, calcification and lipid. The results for derived sound speed in the adapted TMM were consistently close to the expected value of soft tissue, 1540 ms-1. The fibrous tissue showed a mean value of 1584 ms-1 at body temperature, 37oC. The derived sound speeds for elastic and lipid exhibited large inter-quartile ranges. The calcification had a significantly higher sound speed than the other plaque components at 1760 - 2000 ms-1.

This master’s thesis deals with the construction and realization of an ultrasound anemo- meter. Individual types of anemometers are compared in this thesis, including mechanical, thermo anemometer and ultrasound anemometer. Different construction renderings and measurement principles of ultrasonic anemometers are analyzed. In addition, an experi- mental method of measuring the speed of sound by phase shift between two transmitting frequency is described in the document. This thesis includes the design of an control unit and the realization of a simple prototype of an ultrasonic anemometer. Experimental confirmation of the characteristics of the ultrasound anemometer is the last part of the document.

L'objectif de cette thèse consiste en l'étude d'une stratégie de contrôle actif à faible autorité avec comme application le contrôle actif du rayonnement acoustique d'une plaque. Depuis l'essor du contrôle actif, son application aux problèmes acoustiques et vibracoustiques a été investiguée par de nombreux chercheurs, exploitant soit la théorie du contrôle optimal, soit des approches originales basées plus particulièrement sur la physique. Des notions spécifiques au contrôle vibroacoustique ont été développées comme, par exemple, les modes radiatifs pouvant caractériser le rayonnement acoustique d'une plaque d'une manière adaptée au contrôle.

Le contrôle actif à faible autorité, pour lequel le Laboratoire de Structures Actives a développé une expertise dans le domaine de l'amortissement et du contrôle actif des vibrations, est une solution attractive par sa simplicité de mise en oeuvre. Le plus souvent implémenté sous la forme d'un contrôle décentralisé constitué de boucles indépendantes, le contrôle à faible autorité bénéficie de certaines garanties de stabilité et de robustesse.

Bien que notre stratégie de contrôle puisse s'appliquer à n'importe quel type de plaque, l'application considérée dans ce travail a été motivée par le contexte socio-économique actuel en rapport avec les nuisances acoustiques. Il était en effet intéressant d'évaluer la stratégie de contrôle pour le problème de la transmission acoustique d'un vitrage. La stratégie de contrôle se divise en deux étapes. Tout d'abord le développement d'un capteur unique destiné à fournir une mesure représentative du bruit rayonné par une plaque en basse fréquence. Deux capteurs de vitesse volumétrique (l'un discret, l'autre distribué) ont ainsi été développés et évalués expérimentalement.

Ensuite, une procédure d'optimisation de l'emplacement d'un ensemble d'actionneurs pilotés en parallèle est proposée. L'objectif de cette phase d'optimisation est de forcer la réponse fréquentielle du système à posséder les propriétés d'un système colocalisé. La stratégie de contrôle est ensuite évaluée sur deux structures expérimentales.

/ This thesis is concerned with a low authority active control strategy applied to the sound radiation control of a baffled plate. Since the development of active control ,numerous researchers have studied its application to acoustical or vibroacoustical problems using either the modern control theory or other methods based rather on the understanding of the physics of the problem. Vibroacoustical active control has lead to the definition of radiation modes allowing to describe the radiated sound of a plate in an appropriate manner for active control purposes.

Low autorithy control (LAC), for which the Active Structures Laboratory has gained an expertise for active vibration control applications is an interesting solution for its implementation simplicity. Most of the time it consists of several decentralized control loops, and benefits from guaranteed stability and robustness properties. Although our control strategy can be applied to any kind of plates, the application considered here has been motivated by the present socio-economical context related to noise annoyances. The active control strategy has been applied the problem of the sound transmission loss of glass plates (windows). This strategy is in two steps :first a volume velocity sensor is developed as to give a measure representative of the radiated sound at low frequencies.

Two sensors have been developed (one discrete and one distributed) and experimentally tested. Next, an optimisation strategy is proposed which allow to locate on the plate a set of several actuators driven in parallel. The goal of this optimisation task is to obtain an open-loop frequency response which behave like a collocated system. The control strategy is finally evaluated on two plate structures.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

Thesis (S.M. in Electrical Engineering and Computer Science)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 113-114).
Current underwater acoustic channel estimation techniques generally apply linear MMSE estimation. This approach is optimal in a mean square error sense under the assumption that the impulse response fluctuations are well characterized by Gaussian statistics, leading to a Rayleigh distributed envelope. However, the envelope statistics of the underwater acoustic communication channel are often better modeled by the K-distribution. In this thesis, by presenting and analyzing field data to support this claim, I demonstrate the need to investigate channel estimation algorithms that exploit K-distributed fading statistics. The impact that environmental conditions and system parameters have on the resulting distribution are analyzed. In doing so, the shape parameter of the K-distribution is found to be correlated with the source-to-receiver distance, bandwidth, and wave height. Next, simulations of the scattering behavior are carried out in order to gain insight into the physical mechanism that cause these statistics to arise. Finally, MAP and MMSE based algorithms are derived assuming K-distributed fading models. The implementation of these estimation algorithms on simulated data demonstrates an improvement in performance over linear MMSE estimation.
by Alison Beth Laferriere.
S.M.in Electrical Engineering and Computer Science

Avfallseldade kraftvärmeverk får idag betalt för att ta emot och elda avfall. Dessa intäkter är ofta högre än intäkterna från elproduktion och värmeproduktion så man vill under de flesta förhållanden elda så mycket som det är möjligt. För att göra sig av överskottseffekten som kan uppstå kyler man bort det man inte behöver. Nybro Energis kraftvärmeverk i Transtorp använder sig utav 6 stycken kylpaket med 4 fläktar på varje för att kunna kyla bort denna överskottseffekt. Vid installeringen var målsättningen att kunna kyla bort 10MW men det visade sig att under sommaren när utomhustemperaturen blev högre kunde kyleffekten gå ner till 7MW. Vår undersöknings syfte var att med en ny motor med ett högre cos α göra tester på en av fläktarna och se om man kan öka kyleffekten och få ner förbrukningen på motorerna utan att kylpaketen ska ge ifrån sig högre ljudnivåer än tidigare. Ett alternativ till att enbart sänka strömförbrukningen för den befintliga motorn är att faskompensera och det framgick att elförbrukningen gick att sänka från 8.2A till 3.88A. Det framgick att den nya motorn när den frekvensstyrs på 40hz drar högre aktiv effekt men avsevärt mindre reaktiv effekt som gör den billigare i drift. Under mätningarna för att få fram kyleffekten uppmättes tvivelaktiga värden som visade att den kylde sämre på 40hz än den tidigare motorn trots ett högre varvtal. Detta stämmer inte teoretiskt och det är orimligt att den inte kommer kyla. På 40hz kommer den nya motorn även att ge ifrån sig mindre ljud. Detta trots att en fläkt ska låta mer på ett högre varvtal det konstaterades att bullret från själva motorn är lägre i den nya motorn. Går man upp i frekvens till 50hz och räknar med 28 stycken nya motorer få man en ljudökning på 5dB på 300m jämfört med den gamla motorn. Denna går att sänka 3dB om man lyckas eliminera den intilliggande väggens ljudreflekterande egenskaper. Den nya motorn rekommenderas då den har många fördelar och vill man köra på högre frekvenser kan man med fördel använda sig utav ljudabsorbenter längs väggen för att eliminera dennas dubblerande effekt på ljudnivån.
Waste-cogeneration plants are paid today to receive and burn waste. These revenues are often higher than the revenues from electricity generation and heat production, so you want to burn as much as possible in most circumstances. In order to take advantage of the surplus effect that may occur, it eliminates what you do not need. Nybro Energi's CHP plant in Transtorp uses 6 cooling packs with 4 fans on each in order to cool off this excess power. During installation, the goal was to be able to cool off 10MW but it turned out that during summer when the outdoor temperature became higher, the cooling power could go down to 7MW. Our purpose of investigation was to use a new engine with a higher cos α to test on one of the fans and see if you can increase the cooling power and reduce the consumption of the engines without the cooling packages giving higher noise levels than before. An alternative to only reducing the current on the old motor is to phase compensate and according to calculations the motors current can be reduces from 8.2A to 3.88A. It was found that the new engine when frequency controlled at 40hz pulls higher active power but significantly less reactive power that makes it cheaper in operation. During the measurements to obtain the cooling effect, doubtful values ​​were measured which showed that it cooled worse at 40hz than the previous engine despite a higher fan speed. This is not correct theoretically and it is unreasonable that it will not cool better but a figure exactly how much could not be produced. At 40hz, the new engine will also produce less noise if you choose to replace all 28 engines. This despite the fact that a fan is going to run more at a higher speed, it was found that the noise from the engine itself is lower in the new engine. If you go up to 50hz frequency and expect 28 new engines, you'll get a sound boost of 5dB at 300m compared to the old engine. This can be lowered by 3dB if you manage to eliminate the properties of the adjacent wall sound reflectors. The new engine is recommended as it has many advantages and if you want to drive at higher frequencies, you can advantageously use sound absorbers along the wall to eliminate its double effect on the noise level.

The objective of this project was to provide reliable thermophysical property data, mainly density and sound speed, for industrial and academic use. This thesis investigates in detail the speed of sound and density of several industrial fluids at pressure up to 400 MPa and temperature from 248 K to 473 K. The experimental technique used was based on an ultrasonic cell implementing a double-path pulse-echo method with an ultrasound transducer placed between two unequally-spaced reflectors. The cell was calibrated in water at T = 298.15 K and p = 1 MPa against the speed of sound given by the 1995 equation-of-state formulation of the International Association for the Properties of Water and Steam (IAPWS-95) which, for that state point, has an uncertainty of ± 0.005 %. In this thesis, the ultrasonic cell was validated by water measurement over a wide range of temperature and pressure and was shown to have an uncertainty of ± 0.03 %. The uncertainty of the sound speed measurement for other fluids in general is less than 0.1 %. In addition, a densimeter was also used. The measured sound speed and density combined with the heat capacity can be used to develop advanced analytical equations of state and derive all of the thermodynamic properties for key mixtures by numerical-integration algorithms. All the thermophysical properties measured in this thesis were correlated into equations as a function of temperature and pressure. The correlated parameters were calculated by regression analysis in Microsoft Excel. The regression function is used to minimize the sum of squares of error of all the data which needs to be fitted into an equation. In our regression analysis from Excel, the objective was to fit the data to within the target uncertainty using the number of parameters required. Several working fluids were studied: pure water, hexafluoropropene (HFP), trifluoro-3-(trifluoromethyl)oxirane (common name hexafluoropropylene oxide, HFPO), carbon dioxide, and carbon dioxide + propane mixtures. The results extend our understanding of the thermophysical properties of these key industrial fluids and may lead to the development of improved thermodynamic models for application in air conditioning, refrigeration system and carbon capture and storage applications.

The developments of new types of conductors and increase of voltage level have driven the need to carry out research on evaluating overhead line acoustic noise. The surface potential gradient of a conductor is a critical design parameter for planning overhead lines, as it determines the level of corona loss (CL), radio interference (RI), and audible noise (AN). The majority of existing models for surface gradient calculation are based on analytical methods which restrict their application in simulating complex surface geometries. This thesis proposes a novel method which utilizes both analytical and numerical procedures to predict the surface gradient. Stranding shape, proximity of tower, protrusions and bundle arrangements are considered within this model. One of UK National Grid's transmission line configurations has been selected as an example to compare the results for different methods. The different stranding shapes are a key variable in determining dry surface fields. The dynamic behaviour of water droplets subject to AC electric fields is investigated by experiment and finite element modelling. The motion of a water droplet is considered on the surface of a metallic sphere. To understand the consequences of vibration, the FEA model is introduced to study the dynamics of a single droplet in terms of phase shift between vibration and exciting voltage. Moreover, the evolution of electric field within the whole cycle of vibration is investigated. The profile of the electric field and the characteristics of mechanical vibration are evaluated. Surprisingly the phase shift between these characteristics results in the maximum field occurring when the droplet is in a flattened profile rather than when it is ‘pointed’.Research work on audible noise emitted from overhead line conductors is reviewed, and a unique experimental set up employing a semi-anechoic chamber and corona cage is described. Acoustically, this facility isolates undesirable background noise and provides a free-field test space inside the anechoic chamber. Electrically, the corona cage simulates a 3 m section of 400 kV overhead line conductors by achieving the equivalent surface gradient. UV imaging, acoustic measurements and a partial discharge detection system are employed as instrumentation. The acoustic and electrical performance is demonstrated through a series of experiments. Results are discussed, and the mechanisms for acoustic noise are considered. A strategy for evaluating the noise emission level for overhead line conductors is developed. Comments are made on predicting acoustic noise from overhead lines. The technical achievements of this thesis are summarized in three aspects. First of all, an FEA model is developed to calculate the surface electric field for overhead line conductors and this has been demonstrated as an efficient tool for power utilities in computing surface electric field especially for dry condition. The second achievement is the droplet vibration study which describes the droplets' behaviour under rain conditions, such as the phase shift between the voltage and the vibration magnitude, the ejection phenomena and the electric field enhancement due to the shape change of droplets. The third contribution is the development of a standardized procedure in assessing noise emission level and the characteristics of noise emissions for various types of existing conductors in National Grid.

This thesis is concerned with the development and application of laser induced thermal grating spectroscopy (LITGS) as a tool for thermometry in reacting and non-reacting flows. LITGS signals, which require resonant excitation of an absorbing species in the measurement region to produce a thermal grating, are acquired for systematic measurements of temperature in high pressure flames using OH and NO as target absorbing species in the burned gas. The signal obtained in LITGS measurements appears in the form of a time-based signal with a characteristic frequency proportional to the value or the sound speed of the local medium. With knowledge of the gas composition, the temperature can be derived from the speed of sound measurement. LITGS thermometry using resonant excitation of OH in the burned gas region of in oxygen enriched CH4/O2/N2 and CH4/air laminar flames was performed at elevated pressure (0.5 MPa) for a range of conditions. Measurements were acquired in oxygen enriched flames to provide an environment in which to demonstrate LITGS thermometry under high temperature conditions (up to 2900 K). The primary parameters that influence the quality of LITGS signal were also investigated. The signal contrast, which acts as a marker for the strength of the frequency oscillations, is shown to increase with an increase in the burnt gas density at the measurement point. LITGS employing resonant excitation of NO is also demonstrated for quantitative measurements of temperature in three environments – a static pressure cell at ambient temperature, a non-reacting heated jet at ambient pressure and a laminar premixed CH4/NH3/air flame operating at 0.5 MPa. Flame temperature measurements were acquired at various locations in the burned gas close to a water-cooled stagnation plate, demonstrating the capability of NO-LITGS thermometry for measuring the spatial distribution of temperature in combustion environments. In addition, the parameters that in influence the local temperature rise due to LITGS were also investigated in continuous vapour flows of acetone/air and toluene/air mixtures at atmospheric conditions. Acetone and toluene are commonly targeted species in previous LITGS measurements due to their favourable absorption characteristics. Results indicate that LITGS has the potential to produce accurate and precise measurements of temperature in non-reacting flows, but that the product of the pump intensity at the probe volume and the absorber concentration must remain relatively low to avoid significant localised heating of the measurement region.

碩士
國立中山大學
海下科技暨應用海洋物理研究所
101
Plate motions over the past few million years have averaged 1 10 centimeters per year. To monitor such slight deformations in the crust by the GPS/Acoustic geodesy, the accuracy on the order of a few centimeters in positioning seafloor transponders is required. Temporal and spatial variability of sound speed in the water column, however, as well as the measurement error of sound speed, is a main limiting factor in the production of accurate acoustic ranging even though frequent conductivity-temperature-depth (CTD) casts are made. Therefore, in this study, various geometrical options for acoustic ranging are designed in the numerical simulation of GPS/Acoustic geodesy and the effects of various sound-speed measurement errors on the accuracy of transponder positioning are evaluated. The simulation results show that observing slant-range measurements symmetrically around the transponder can nullify sound-speed errors in the horizontal but not vertical positioning of a seafloor transponder. Sound-speed errors produce the vertical positioning error although the slant-range observations are well geometrically balanced. For reducing the effect of sound-speed variation on the precision of GPS/Acoustic seafloor geodesy, this study proposes two synthetic sound-speed profiles of the water column, one linear and the other bilinear, to approximate acoustic travel-time measurements. The approximating sound-speed profile is used in combination with the tomographic estimation in GPS/Acoustic geodesy to estimate the sound speed variation, such that the effect of sound speed variation on the accuracy of transponder positioning is reduced. The performance of the two synthetic models is evaluated for different types of CTD-derived sound-speed profiles and for the acoustic ranging observations collected from a field GPS/Acoustic survey. The evaluation results demonstrate that both the linear and bilinear models can effectively reduce the effect of sound-speed variation on the precision of GPS/Acoustic positioning.

The pressure increase attributed to the energy deposition in the liquid metal target of the Spallation Neutron Source results in cavitation and pitting erosion of the target pressure boundary. Introducing compressibility in the form of small gas bubbles will extend the lifetime of the target vessel. The pressure rise caused by the beam energy deposition occurs in one microsecond, which encourages use of bubbles of radius less than 20 microns, such that the bubble response to pressure change is adequately fast. Gas volume fraction near 0.5% is sufficient to accommodate the mercury volumetric expansion and reduce the pressure rise. Bubble production and detection technologies are developed herein to allow control of the bubble diameter and volume fraction in an opaque liquid metal. This research infers bubble size in the form of a probability density function using dynamic gas delivery pressure and mass flow, and passive acoustic emissions at bubble birth, for a single orifice bubbler. Terminal rise velocities are also measured and used to infer bubble diameter. The gas volume fraction is inferred from the acoustic sound speed using the so-called low frequency Wood’s Limit model for sound speed in a bubbly media.

This thesis is part of the project undertaken to develop a diffusive acoustic confocal imaging system (DACI) that aims to differentiate between healthy and the diseased tissues in the prostate. Speed of sound is chosen as the tool to quantify the alterations in the tissues’ mechanical properties at different pathological states. The current work presents a scanning configuration that features three components: an acoustic emitter, a focusing mirror and a point receiver. The focusing mirror brings the collimated acoustic beam from the emitter into a focused probe position, which needs to be located within the bladder or at the near surface of the prostate. This position is introduced as the virtual source, where the acoustic intensity diffusively scatters into all directions and propagates through the specimen. The system design was simulated using ZEMAX and COMSOL to validate the concept of the virtual source. Lesions in a phantom prostate were found in the simulated amplitude and phase images. The speed of sound variation was estimated from the 1D unwrapped phase distribution indicating where the phase discontinuities existed. The measurements were conducted in a water aquarium using the tissue-mimicking prostate phantom. Two-dimensional projected images of the amplitude and the phase distributions of the investigating acoustic beam were measured. A USRP device was set up as the signal generation and acquisition device for the experiment. Two different signal extractions methods were developed to extract the amplitude and the phase information. The experimental results were found to generally agree with the simulation results. The proof-of-concept design was successful in measuring both the phase and the amplitude information of the acoustic signal passing through the prostate phantom. In future, the 2D/3D speed of sound variation needs to be estimated by an appropriate image reconstruction method.
Graduate
2018-12-06

Given the interest on underwater axisymmetric cylindrical bodies for the development of high-speed underwater weapons, characterization of the boundary layer flow-induced noise received by a Sound NAvigation and Ranging (SONAR) is very important to improve sonar detection ranges. The debate on generating mechanisms of the flow induced noise received at the stagnation point is still on as there is no experimental evidence conclusively suggesting whether it is a near-field or far-field phenomenon, thereby introducing an element of uncertainty in the prediction models. Further, the models developed thus far were based on low Reynolds numbers involving flows in water tunnels and buoyant vehicles. Therefore, the main focus of the thesis is to measure the flow induced noise using a sonar fitted at the most forward stagnation point of an underwater axisymmetric body as realistically as possible and predict the same theoretically for identifying a suitable flow noise model for future use by designers. In order to meet the stated goal, two exclusive experiments were conducted at sea using an underwater autonomous high-speed axisymmetric vehicle fitted with a planar hydrophone array (8X8) in its nose cone which measured the flow noise signature. Two different sets of existing models are used in characterizing the flow noise received by the array, while the first set comprises of models developed based on the Turbulent Boundary Layer induced noise and other is based on the transition zone radiated noise model. Through this study, it was found that the transition zone radiated noise model is in close agreement with the measured data.

The propagation of acoustic waves through water-saturated granular sediments has been widely studied, yet existing propagation models can not adequately predict the speed and attenuation of sound across the range of frequencies of interest in underwater acoustics, especially in loosely packed sediments that have been recently disturbed by storms or wave action. Advances in modeling are currently dependent on experimental validation of various components of existing models. To begin to address these deficiencies, three well-controlled laboratory experiments were performed in gravity-settled glass beads and reconstituted sand sediments. Sound speed and attenuation measurements in the 0.5 kHz to 10 kHz range are scarce in the literature, so a resonator method was used to investigate a reconstituted sand sediment in this range. The literature contains laboratory and in situ measurements of sound speed and attenuation at higher frequencies, but existing models can not predict both the speed of sound and attenuation simultaneously in some sediments. A time-of-flight technique was used to determine the speed of sound and attenuation in monodisperse water-saturated glass beads, binary glass bead mixtures, and reconstituted sediment samples in the frequency range 200 kHz to 900 kHz to investigate the effect of sediment inhomogeneity. The effect of porosity, independent of changes in other sediment physical properties, has not been demonstrated in the experimental literature. Therefore, a fluidized bed technique was used to independently vary the porosity of monodisperse glass bead samples from 0.37 to 0.43 and a Fourier phase technique was used to determine the speed and attenuation of sound. Collecting these results together, measured sound speeds showed positive dispersion below 50 kHz while negative dispersion was observed above 200 kHz for some samples. Attenuation measurements showed an approximately f⁰̇⁵ dependence in the low frequency regime and an approximately f³̇⁵ dependence for large-grained samples in the high frequency regime. The laboratory experiments presented in this work demonstrate that both sound speed and attenuation in idealized loosely packed water-saturated sediments can not be simultaneously predicted by existing models within the uncertainties of the model input parameters, but the independent effect of porosity on sound speed can be predicted.
text